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At least 19 recordsLinked to original sources
USGS1983

Expendable bubble tiltmeter for geophysical monitoring

An unusually rugged highly sensitive and inexpensive bubble tiltmeter has been designed, tested, and built in quantity. These tiltmeters are presently used on two volcanoes and an Alaskan glacier, where they continuously monitor surface tilts of geological interest. This paper discusses the mechanical, thermal, and electric details of the meter, and illustrates its performance characteristics in both large (>10-4 radian) and small (<10-6 radian) tilt environments. The meter's ultimate sensitivity is better than 2??10-8 radians rms for short periods (hours), and its useful dynamic range is greater than 10 4. Included is a short description of field use of the instrument for volcano monitoring.

Review of Scientific Instruments↗
USGS2012

Note: Rotaphone, a new self-calibrated six-degree-of-freedom seismic sensor

We have developed and tested (calibration, linearity, and cross-axis errors) a new six-degree-of-freedom mechanical seismic sensor for collocated measurements of three translational and three rotational ground motion velocity components. The device consists of standard geophones arranged in parallel pairs to detect spatial gradients. The instrument operates in a high-frequency range (above the natural frequency of the geophones, 4.5 Hz). Its theoretical sensitivity limit in this range is 10(-9) m/s in ground velocity and 10(-9) rad/s in rotation rate. Small size and weight, and easy installation and maintenance make the instrument useful for local-earthquake recording and seismic prospecting.

Review of Scientific Instruments↗
USGS1982

Portable precision dc voltage-current transfer standard for electrometer calibration

A circuit design is presented for an instrument providing a highly stable and fully adjustable voltage and current in the range of 0-1.999 V or 0-199.9 mV and 10-11-10-15 A. This instrument is used to verify the calibration and performance of dc and vibrating reed electrometers and chart recorders on mass spectrometers of the USGS Isotope Laboratories in Denver.

Review of Scientific Instruments↗
USGS2001

Measurement of gas yields and flow rates using a custom flowmeter

A simple gas collection apparatus based on the principles of a Torricelli tube has been designed and built to measure gas volume yields and flow rates. This instrument is routinely used to monitor and collect methane gas released during methane hydrate dissociation experiments. It is easily and inexpensively built, operates at ambient pressures and temperatures, and measures gas volumes of up to 7 L to a precision of about 15 ml (about 0.0025 mol). It is capable of measuring gas flow rates varying from more than 103 to less than 10-1 ml/min during gas evolution events that span minutes to several days. We have obtained a highly reproducible hydrate number of n=5.891 with a propagated uncertainty of ??0.020 for synthetic methane hydrate. ?? 2001 American Institute of Physics.

Review of Scientific Instruments↗
USGS1981

Improved spectrophotometric cell for hydrothermal solutions

A simple, inexpensive spectrophotometric cell was designed for use with aqueous solutions for which temperature is a maximum of 325??C and pressure, 28 MPa. The cell has an internal volume of 5 ml and a path length of 1.31 cm. Each furnace assembly is 120 mm in diameter ?? 150 mm high and will fit into most commercial spectrophotometers. Temperature is controlled by a standard set-point controller and a balancing circuit that is used to maintain the temperature of the sample and reference cell within 1??C of each other at any temperature.

Review of Scientific Instruments↗
USGS1988

Description and testing of three moisture sensors for measuring surface wetness on carbonate building stones

Three moisture sensors were tested as a means for determining the surface wetness on carbonate building stones exposed to conditions that produce deposition of moisture. A relative-humidity probe, a gypsum-coated circuit grid, and a limestone-block resistor were tested as sensors for determining surface wetness. Sensors were tested under laboratory conditions of constant relative humidity and temperature and also under on-site conditions of variable relative humidity and temperature for eight weeks at Newcomb, NY. Laboratory tests indicated that relative humidity alone did not cause sensors to become saturated with water. However, the rates of drying indicated by the sensors after an initial saturation were inversely related to the relative humidity. On-site testing of the relative-humidity probe and the gypsum-coated ciruit grid indicated that they respond to a diurnal wetting and drying cycle; the limestone-block resistor responded only to rainfall.

Review of Scientific Instruments↗
USGS1993

A new diamond anvil cell for hydrothermal studies to 2.5 GPa and from -190 to 1200 °C

A new style of diamond anvil cell(DAC) has been designed and built for conducting research in fluids at pressures to 2.5 GPa and temperatures from &minus;190 to 1200&thinsp;&deg;C. The new DAC has been used for optical microscope observations and synchrotron x‐ray diffraction studies. Fringes produced by interference of laser light reflected from top and bottom anvil faces and from top and bottom sample faces provide a very sensitive means of monitoring the volume of sample chamber and for observing volume and refractive index changes in samples that have resulted from transitions and reactions. X‐ray diffraction patterns of samples under hydrothermal conditions have been made by the energy dispersive method using synchrotron radiation. The new DAC has individual heaters and individual thermocouples for the upper and lower anvils that can be controlled and can maintain temperatures with an accuracy of &plusmn;0.5&thinsp;&deg;C. Low temperatures are achieved by introducing liquid nitrogen directly into the DAC. The equation of state of H 2 O and the &alpha;‐&beta; quartz transition are used to determine pressure with an accuracy of &plusmn;1% in the aqueous samples. The new DAC has been used to redetermine five isochores of H 2 O as well as the dehydration curves of brucite, Mg(OH) 2 , and muscovite, KAl 2 (Si 3 Al)O 10 (OH) 2 .

Review of Scientific Instruments↗
USGS1973

A pneumatic sample changer for gamma-ray spectroscopy

A gravity‐feed, pneumatic‐ejection sample changer has been developed. The changer is suitable for both flat and well‐type detectors and permits the continuous use of gamma‐ray spectroscopy equipment 24 h a day, 7 days a week. The electronic circuitry has a fail‐safe feature which stops the operation of the changer if a malfunction occurs.

Review of Scientific Instruments↗
USGS1958

Quartz helix magnetic susceptibility balance using the Curie-Cheneveau principle

A quartz spring balance is described which can be used to measure the magnetic susceptibility of submilligram amounts of sample. The magnetic field is supplied by a moving permanent magnet, and the susceptibility is determined by the deflection of the spring observed in a measuring microscope. The apparatus is calibrated by a comparison standard (platinum) and results are shown for platinum, nickel aluminate, lead, manganese, and sucrose. A precision of better than 2% can be obtained on submilligram amounts of paramagnetic substances having a magnetic susceptibility of from 1 to 50×10 −6 emu/g. On weakly paramagnetic or diamagnetic substances comparable precision can be obtained on less than 10 mg amounts of sample.

Review of Scientific Instruments↗
USGS1959

Absolute method of measuring magnetic susceptibility

An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved.

Review of Scientific Instruments↗
USGS1960

Effect of crystal thickness and geometry on the alpha-particle resolution of CsI (Tl)

The resolution of CsI(Tl) for Po 210 alpha particles has been measured as a function of crystal thickness. The best resolution of a ½‐in. diam cylindrical crystal was obtained for a thickness of 0.38 mm, and the effect of thickness on the resolution is discussed. Based on the proposed model, a conical crystal was designed, which yielded a line width of 1.8% for Po 210 alpha particles with a selected photomultiplier tube.

Review of Scientific Instruments↗
USGS1962

Temperature dependence of decay time and intensity of alpha pulses in pure and thallium-activated cesium iodide

The intensity and decay time of Po 210 alpha particle scintillations produced in pure and thallium‐activated cesium iodide have been measured with a fast electronic system as a function of temperature down to 77°K. Three modes of decay due to alpha excitation have been observed for CsI(Tl), and two for CsI. Other than the 7‐ and 0.55‐μsec modes (at room temperature) reported in the literature for CsI(Tl), an additional temperature‐independent mode of about 1.3 μsec has been detected between 77 and 150°K. In CsI a fast temperature‐dependent mode of decay (≈100 nsec) was observed between 100–200°K in addition to the known principal mode.

Review of Scientific Instruments↗
USGS1965

Vacuum-jacketed hydrofluoric acid solution calorimeter

A vacuum‐jacketed metal calorimeter for determining heats of solution in aqueous HF was constructed. The reaction vessel was made of copper and was heavily gold plated. The calorimeter has a cooling constant of 0.6 cal‐deg −1 ‐min −1 , approximately ¼ that of the air‐jacketed calorimeters most commonly used with HF. It reaches equilibrium within 10 min after turning off the heater current. Measurements of the heat of solution of reagent grade KCl(−100 mesh dried 2 h at 200°C) at a mole ratio of 1 KCl to 200 H 2 O gave Δ H = 4198±11 cal at 25°C.

Review of Scientific Instruments↗